In the summer of 2004, Cardinal Joseph Ratzinger wrote a confidential letter addressing one of the most controversial doctrinal issues involving Catholic faith and public life.

We are talking, of course, about whether it is wise for Catholic clergy to deny Holy Communion to Catholic politicians who consistently and openly reject centuries of church teachings on abortion, marriage and other hot-button doctrinal issues.

On one side of this fight are Catholics who say priests should take this stance in an attempt to encourage politicians to confess their sins and receive forgiveness. The goal is to save souls.

On the other side are Catholic progressives (for the most part) who say priests almost always use this tactic to punish Democrats who clash with the church on abortion, while declining to punish Republicans (for the most part) who clash with the church on issues such as the death penalty, immigration, etc., etc.

This is the tip of a giant iceberg, of course, and the cardinal who would then become Pope Benedict XVI has made other statements on this issue. It didn’t help that, at a key moment, then Cardinal Theodore McCarrick blurred (that’s putting things mildly) some of the details of Ratzinger’s 2004 letter.

Why bring this up? All of this is crucial background material for a spectacular online clash between a famous Catholic scholar and editors at The Providence Journal about a truly bizarre story (“Priest: No Communion for R.I. lawmakers who supported abortion law”).

Where to begin? First, let’s flash back to a 2007 National Catholic Reporter story about that Ratzinger letter — “Worthiness to Receive Holy Communion.”

“There may be a legitimate diversity of opinion even among Catholics about waging war and applying the death penalty, but not however with regard to abortion and euthanasia,” Ratzinger wrote.